Image guided drug and therapy delivery is used to optimize therapeutic delivery to a given diseased area. Standard fluoroscopy, MR, CT, and ultrasound have been used for a number of years to perform guided biopsies and delivery of drugs to a variety of locations in the body. See, for example, Mullar D A, Carrasco C H, Katz R L, et al., “FNAB: the role of immediate cytologic assessment,” American Journal of Roentgenology 1986; 147:155-58; Moullen I S, Merc P R., “Percutaneous coaxial biopsy technique with automated biopsy needle—value in improving accuracy and negative predictive value” Radiology 1993; 186:515-22; Zinzani P L, Colecchia A, Fest D, et al., “US guided core needle biopsy is effective in initial diagnosis of lymphoma” Hematologica 1998; 83:989-92; Mouton J S, Leoni C J, Quarfardt S D, Woth S., “Percutaneous image guided biopsy” In Baum S, Pentcort M (ed). Abrams Angiography: Interventional Radiology, 2nd edition, Lippincot William Wilkins, 2006. Philadelphia, pp 255-78; Prashant, Ramachandra C Pattbhiraman, et al., “Feasibility, Safety, and efficacy of the CT guided Fine needle aspiration cytology (FNAC) of lung lesions” Ind J Med & Paed Oncol 2007; 28:16.
These modalities are anatomical in nature, namely, they represent the physical state of the tissue, not its functional state. Emission computed tomography imaging modalities such as Positron Emission Tomography (PET) represent the function of the tissue, and can present more information to the clinician. For example, within a cancerous tumor, anatomically, the center is no different than the outer edges, but depending on the type of cancer, it may in fact be necrotic. Samples taken from this area may produce erroneous results. This means that simply targeting the larger central portion of the tumor is not adequate in all cases. FluoroDeoxyGlucose (FDG) studies done with PET can differentiate between necrotic and active areas of a cancerous tumor.
Traditional image-guided navigation systems have relied on tracking of the instrument and images taken prior to the procedure to guide the instrument to a particular place. MR, CT, fluoroscopic, PET and other types of images have been used. However, soft-tissue in many parts of the body rarely remains in the same location when the patient is moved. Indeed, the instrument itself can sometimes displace the tissue enough to miss the target. If guidance down to a millimeter is desired, traditional image-based navigation systems therefore may not be suitable for at least some types of procedures.
It has been hypothesized that by injecting the patient with FDG, and using a needle that is coated with a positron emitting radioisotope, PET can be used to guide the needle directly to the diseased area. Once properly located, a biopsy sample can be taken, or a therapeutic can be delivered. The PET breast imaging company, Naviscan, has done work along these lines. See Xiaohong, Anashkin, Matthews, Weidong, Real-Time Viewer for Positron Emission Mammography Guided Biopsy, IEEE Transactions on Nuclear Science, 57:3, June 2010, pp. 1139-1145. Its approach uses fixation, and it is very approximate.
It is not necessary to guide a physical device to deliver a therapeutic. In fact, radiation therapy can perform similar therapeutic delivery, and the use of PET scans to plan radiation therapy is standard practice. See Gregoire V, Haustermans K, Geets X, et al., “PET-based treatment planning in radiotherapy: a new standard?” J Nuc. Med. 2007; 48:68S-77S. Some radiation treatment techniques, namely proton therapy, are powerful enough that they activate Carbon, Nitrogen, and Oxygen atoms as they pass through the body. As these activated isotopes decay, some of them give off positrons which can be imaged with PET. Thus, it is theoretically possible to see the effect of proton therapy with PET, and relate the location of the activated isotopes with the delivery of therapeutic radiation.
Due to difficulties steering the proton beam, as mentioned by Peterson, Polf, Ciangaru, Frank, Bues, Smith, “Variations in proton scanned beam dose delivery due to uncertainties in magnetic beam steering” Med. Phys., 36(8), 2009, pp. 3693-3702, it is desirable to perform an incremental approach to this type of therapy. The presence of bone, fat, muscle, and metal implants can substantially alter the beam path, causing the beam to miss the target. In this method, a theoretically computed beam profile of very low dose would be initially performed. Once the resulting PET scan identified the actual target, the beam parameters could be altered to steer the beam through the body to the ideal location without regard to distortion. Feedback during the process would keep the beam on the precise target.